Two types of acoustic transducers commonly used today are piezoelectric and magnetostrictive. Because of their high electromechanical coupling coefficient, piezoelectric materials have been used for most high power, broadband applications. The use of piezoelectric materials is limited, however, because they are fragile and tend to deteriorate with use. Because of their ruggedness, it would be advantageous to produce transducers from magnetostrictive metals in lieu of piezoelectric materials. A magnetostrictive metal can be used as a transducer because such a material will undergo mechanical motion when subjected to a magnetic field. In other words, electromagnetic energy can be converted to mechanical energy. For example, if magnetostrictive material shaped as a rod having the length 1 is subjected to a magnetic field, the length of the rod will change from 1 to 1+.DELTA.1. Conversely, any change in length will cause a change in the intensity of the magnetic field. For this reason magnetostrictive devices are useful as acoustic transducers in SONAR systems.
To be useful in high power, broadband applications, the change in length, .DELTA.1, must be large while the magnetocrystalline anisotropy coefficient is low. In order to normalize any measurements made of .DELTA.1, such measurements are merely divided by the length of the rod, 1. .DELTA.1/1 is known as the magnetostrictive strain, .lambda., of the material. When the material is placed in a saturation magnetic field, .DELTA.1/1 is known as the saturation magnetostrictive strain, .lambda..sub.s.
Past efforts to produce better magnetostrictive materials have centered primarily on the 3d transition metal alloy systems Ni-Co-Cr, Fe-Co and Fe-Al. .lambda..sub.s for these materials is about 150.times.10.sup.-6 with very low anisotropy. This invention relates to the formation of magnetostrictive devices from materials capable of similar or even larger magnetostrictive strains than that of current materials being used.